Vibrator



Aug. 20, 1935. H. M. DRESSEL I VIBRATOR Filed July 18, 1934 luvtmoxz I}SNRYM.DRESSEL BY #2 C 161% ATTGRNEY the greater the self-induced potential.

Patented Aug. 20, 1935 PATENT, OFFICE vnms'roa "Henry M. Dressel, Chicago, 111., assignor to Oak Manufacturing Company, Chicago, Ill.

application July 13, 1334, Serial No. 735,135

3 Claims. (01. 172-126) This invention relates to vibrators and has particular application to vibrators used for interrupting a direct current in a system for transforming direct current to alternating current. A system of this character is customarily used in automobile radio systems for obtaining from the 6-volt storage battery; a high potential supply for the vacuum tubes. In a radio receiver of this character it is necessary that a vibrator be simple, cheap, rugged, and have a long useful life.

Arcing of the driving contacts has been a serious problem in vibrators of this type. The slightest pitting of contacts results in a higher potential drop across the contacts when closed and results in erratic and-unsteady performance. Further-- more, contacts frequently become frozen, that is, welded together because of the extremely heavy currents, thus rendering the vibrator completely inoperative.

- The most common and, in fact, thus far, the only practical expedient to eliminate arcing at contacts has been in the use of a condenser and .resistance across the contacts. This however is not entirely satisfactory. An object of this invention is to devise a vibrator in which arcing at the driving contacts is substantially eliminated. Another object is to eliminate such arcing in a simple and cheap manner.

Arcing of the contacts of vibrators is a manifestation of the self-inductance of the magnetic system of the vibrator just at the point when the contacts tend to open and cut the current in the magnetizing coil down to zero. The decay of the magnetic field builds up a counter-electromotive force in the winding and induces a potential which tends to keep the current flowing in the winding in the same direction as before the decay of the field. Obviously the more sudden the break the faster the decay of the field and In a vibrator of this type adapted to operate on about relieve the system of the shock, occasioned when six volts, potentials as high as 100'volts have been measured across the contacts just at the opening. While a condenser 01- a combination of condenserand resistor will cut down arcing somewhat, nevertheless the potential peaks are still present in a large degree, so much so that they must be considered in the breakdown characteristics of the condenser used.

This invention contemplates the provision of a short-circuited winding functioning as a sec-' ondary to the magnetizing coil which serves to thecontacts open. By providing a short-circuited secondary, the decay of the-magnetic field upon the opening of the contacts is delayed, thus delaying the self-induced potential in the winding. In fact, it has been found that the induced potential in the magnetizing coil is the same as the a lied potential.-

Referring to the drawing, Figure 1 is a circuit diagram of a vibrator embodying this invention. Figure 2 is an elevation of a vibrator construction embodying the invention. Figure 3 is a sectional view on line 3-3 of Figure 2 of the vibrator and Figure 4 is a top view oi'the vibrator. Referring to Figure 1 a battery I is connected by a conductor 2 to the middle point 30f a transformer 4. Transformer 4 has windings 5 and 6 comprising the two halves of a centre tapped primary. windings 5 and 6 have their terminals connected by wires 1 and 8, to stationary con-'- tacts 9 and I0 of.a vibrator. Battery I is connected to the vibrator through a switch II to connected by a wire I9 to a magnetizing coil I20.

Coil 20 is connected by a lead 2| to the remote terminal of battery I. In accordance with usual practice, by the cooperation of contacts I! and i9, coil 20 becomes energized to attract armature it toward it. The movement of reed l2 in response to this impulse opens contacts i1 and 16. To prevent arcing, an additional coil 25, having'its terminals connected together to shortcircuit the coil, is provided. This coil is preferably made of the same wire as coil 26, with the wirein both coils alongside of each other. The coils are preferablysimilar with substantially perfect coupling.

Referring to Figure 2 .to 4 inclusive, the vibrator embodying the circuit diagram of Figure 1 is shown. -This vibrator comprises a magnetic member 39, having a bent portion 3|, and an 01!- set 32 and terminating in a pole piece 33. Pole piece 33 carries a spool 34 upon which are wound coils 20 and 25. Terminals 26 and 21 of coil 25 are joined together at the side of the spool. Wire leads l9 and 2i are brought out for connection r to stationary contact l8, and battery I respectively. The inner tip 35 of pole piece 33 has riveted thereto some strips 36 of mica or similar insulating material. Thesestrips preferably extend into the circular space 31 inside the spool and set tightly therein tomaintain the spool 34 rigidly in position. Mica strips 86 have their 5 other ends secured rigidly at 31 to the end 38 of a nonmagnetic bar 40. Both 30 and 40 have their ends aligned and between them there is disposed a plurality-of insulating blocks 4|, 42 and 43. Between these blocks are supported various membersto be hereinafter described. The entire structure has a pair of holes 45 and 48 therethrough, and is provided with insulating bushings 41 and 48 and bolts 49 having heads 50. An insulating'washer 5| is provided to insulate head 50 from member 30 while an insulating washer 52 is provided to insulate nut 53 from member 40. In this way the insulators and the interspersed members are rigidly maintained in predetermined relationship without short-circuiting any of the. metallic members.

Members 30 and 40 each have bolts 55 and 58 threaded therein approximately in the center thereof. These bolts carry fixed contacts 9 and H] respectively at their ends and are maintained by locking nuts 51.

Between insulating members 4| and 42, a metallic supporting member 60 is disposed. This member comprises an elongated spring strip of suflicient thickness to be substantially rigid.

At its free end it carries a spring 8| riveted thereto at 62. Spring 6| carries stationary contact l8, this contact projecting through a suitable aperture in supporting member 60. In this manner, stationary contact I8 is supported on a spring mounting and provided with a rigid stop.

Supported between insulating blocks 42 and-43 is a. reed carrying a magnetizable armature 88 at its free end. Reed 65 at a point a. little above its fixed position has riveted thereto at 81 a pair of spacer blocks 68, 89 and a pair of rigid members 10, H, 12 and 13 upon each side of said spacer blocks. Rigid members 1| and 12 extend upwardly alongside of the reed and are riveted thereto at their upper ends at 15 at a position approximately in line with stationary contacts 9 and I0. Between block 68 and rigid member 18 a spring member I8 is mounted carrying a movable contact 11. This movable contact is adapted to telescope within an aperture in rigid member HI.- A spring member is provided between blocks 88 and rigid member 13 and similar- 1y carries a movable contact 8| telescoping through a suitable aperture in rigid member 18.

It willbe noted that member 18 is longer in extent than member Ill and carries at its free end a movable contact H for controlling magnetizing coil 28.

Between insulating blocks 42 and 43 and adjacent to reed amounting member 85 is provided. This member has a plurality of apertures therethrough into which are disposed rubber grommets 88. A supporting member" has its end adjacent to grommets 86 and the entire vibrator structure is carried by means of the and 88.

netizing coil for energizing said magnetic cir cuit, contacts controlled by said reed for making and breaking said magnetizing coil circuit and a short-circuited winding for reducing the reed amplitude during operation in electro-magnetic relationship to said magnetizing coil said two coils being wound in bifilar relationship and the wires in said two coils being of the same orderof thickness.

2. A vibrator adapted to operate for long periods of time without attention comprising an elongated magnetizable member having a pole piece at one end thereof, means for rigidly supporting said member at its other'end, a reed rigidly supported at said other end of said magnetic member and having a free end adapted to vibrate in proximity to said pole piece, a magnetizing coil carried by said member, contacts order of thickness.

3. A vibrator adapted to operate for long periods of time 'without attention comprising a magnetizable member, having a pole piece at one end thereof, a vibratable reed rigidly supported at one end and having its free end adjacent said pole piece and adapted to vibrate in proximity thereto, a magnetizing coil for said pole piece, a

contact'carried by said reed, a. stationary contact co-operating with said movable contact, connections between said coil and contacts whereby said contacts open and close said magnetizing coil circuit, said reed having a normal position eccentric with respect to said pole piece and with said contacts closed, and a short circuited winding for reducing the reed'amplitude during operation, said windings being wound in bifilar relationship with the wires of saidtwo windings being of the same order of thickness.-

' 4. A vibrator adapted to operate for long periods of time without attention comprising a magnetizable member, having a pole piec e,' a

vibratable reed, rigidly supported at one end and coil whereby said contacts open and close said coil circuit, said reed having a normal position eccentric with respect to said pole piece and with said contacts closed, a pair of additional stationary contacts mounted on each side of said reed, contacts carried by said reed for co-operating'with said additional contacts, and a short circuited winding for reducing the reed amplitude during operation closely coupled with said magnetizing .coil, said short circuited coil and magnetizing coil being wound in bifilar relationship withthe; wires being of the same order of thickness.

5. A vibrator comprising a U-shaped magnetizable structure having a pole piece, a flat spring reed rigidly mounted at one end, within said U carrying an armature in proximity to said pole piece and adapted to vibrate back and forth past said pole piece, a plurality of contacts carried by said reed, said reed having. the contacts mounted on opposite sides thereof, stationary contacts carried by said U-shaped structure on each side of said reed and cooperating with said movable contacts, a magnetizing coil on said U-shaped structure, connections from said coil to certain of said contacts for eilecting p vibration of the armature upon excitation of said coil and an additional short circuited coil for reducing the reed amplitude during operation wound in bifliar relationship to said magnetizing coil. the two coil wires being of substan- 

